Pyrothechnic target

ABSTRACT

According to the invention there is provided an impact initiated pyrotechnic target including an impact initiated pyrotechnic composition which can be initiated by the impact of an inert projectile, said pyrotechnic composition including: an oxidising agent; optionally, a fuel or reducing agent; a sensitiser in the form of a sulfur containing compound; and optionally, a binder.

This invention relates to impact initiated pyrotechnic targets andimpact initiated pyrotechnic compositions.

It is known to provide practice targets for various shooting purposes.For example, targets may be used in conjunction with firearms such asrifles and pistols, and air propelled arms such as air rifles and airpistols. The target may be of the type which is intended to be held in afixed position, and which may have indicia located thereon such as anumber of concentric rings defining a “bullseye”. Alternatively, thetarget may be intended to be used as a moving target such as a “claypigeon”. It is known from U.S. Pat. No. 4,498,677 and WO02/35175 toprovide an explosive target which registers a hit by providing anexplosive event. However, it has proven difficult to produce apyrotechnic which can be satisfactorily ignited by the impact of arelatively low energy projectile such as a pellet or slug discharged bya pneumatic weapon such as an air rifle. Additionally, whilst there is aneed to provide a target which is sufficiently sensitive to provide areaction to a hit by a relatively low energy projectile such as an airgun pellet, the active pyrotechnic used in the target should not be sosensitive as to present a hazard during manufacture, handling orstorage. A related and important consideration is that the nature of theactive pyrotechnic should not render its preparation illegal undernational laws. The laws of the UK are particularly restrictive in termsof the nature of the pyrotechnic and its manufacture. For example, theexplosive formulation described in U.S. Pat. No. 4,498,677 would not belegal under UK law.

The present invention, in at least some of its embodiments, addressesthe above described problems and needs.

According to a first aspect of the invention there is provided an impactinitiated pyrotechnic target including an impact initiated pyrotechniccomposition which can be initiated by the impact of an inert projectile,said pyrotechnic composition including:

an oxidising agent;

optionally, a fuel or reducing agent;

a sensitiser in the form of a sulfur containing compound; and

optionally, a binder.

The sensitiser acts as a source of bound sulfur. This is advantageous,because the sulfur provides an initiation enhancing sensitisation.However, the pyrotechnic composition is safer than compositions whichutilise elemental sulfur by virtue of being chemically bonded to otheratomic constituents of the sensitiser. In this way, the stringent UKlegislation governing pyrotechnics can be satisfied.

Very preferably, the sensitiser is thiourea. Surprisingly, it has beenfound that the presence of thiourea can act as a highly advantageoussensitiser, enabling the provision of a pyrotechnic composition which issufficiently sensitive to provide enhanced impact initiation. A furtheradvantage is that the thiourea can provide an accelerated burn rate. Inat least some embodiments, the use of thiourea can permit impactinitiation by a relatively low energy projectile such as an air rifle orair pistol pellet.

For the avoidance of doubt, the term “inert” as used herein refers to aprojectile which ignites the target by virtue of its kinetic energy onimpact, i.e., a projectile which is non-explosive and does not reactchemically with the pyrotechnic composition.

Preferably, the oxidising agent is a chlorate, most preferably potassiumchlorate.

Advantageously, a fuel or reducing agent is present. Preferably the fuelor reducing agent is charcoal. Other fuels or reducing agents, such asorganic fuels, for example shellac, might be utilised. However, charcoalcan provide excellent results and has the advantage that its use in themanufacture of pyrotechnics in the UK is legal.

Preferred embodiments utilise a chlorate in combination with charcoaland thiourea. A particular preferred combination is potassium chlorate,charcoal and thiourea. It should be noted that the present inventorshave found that mixtures of potassium chlorate and charcoal withoutthiourea were not sensitive enough for use with relatively low energyprojectiles such as air gun pellets at practical firing ranges. It isestimated that the presence of thiourea reduces the ignition temperatureof the potassium chlorate/charcoal pyrotechnic composition by about 200°C., thereby providing greatly enhanced sensitivity to impact initiation.

Whilst it is preferred that a fuel or reducing agent is present inaddition to the thiourea, it may be possible to provide an impactinitiated pyrotechnic composition which does not include a fuel orreducing agent. Tests have revealed that combinations of potassiumchlorate and thiourea (which acts as a fuel and a sensitiser) can becaused to react explosively at temperatures as low as 155° C.

Preferably, the impact initiated pyrotechnic composition includes, byweight, 30-70% of the oxidising agent, 0-60% of the fuel or reducingagent, 8-40% sensitiser and 0-15% of the binder, with the proviso thatthe total weight percentages of these components do not exceed 100%.

Preferably, the impact initiated pyrotechnic composition includes 40-60%by weight of the oxidising agent.

Preferably, the impact initiated pyrotechnic composition includes 20-40%by weight of the fuel or reducing agent.

Preferably, the impact initiated pyrotechnic composition includes 10-40%by weight of thiourea, more preferably 12-30% by weight of sensitiser.

Preferably, the impact initiated pyrotechnic composition includes 1-10%by weight of the binder.

The binder is preferably a resin, such as acaroid resin or shellac.Other suitable binders may be used. In general, the binder is apolymeric matrix of some sort.

The target may further comprise a secondary pyrotechnic compositionwhich is formulated to be initiated by the impact initiated pyrotechniccomposition to produce a desired signalling effect. The desiredsignalling effect may be one or more of an enhanced explosion, a desiredflame colour, enhanced smoke production, a desired noise level oninitiation, a desired burn rate and an incandescent display.

The secondary, pyrotechnic composition can be selected from a wide rangeof suitable candidates in order to provide the desired signallingeffect. In preferred embodiments, the secondary pyrotechnic compositionincludes metal particles and an oxidizing agent. The metal particles maybe aluminium, magnesium or a combination of both.

The secondary pyrotechnic composition may include a suitable binder.

In general, the secondary pyrotechnic composition will include anoxidising agent which is somewhat more stable than the oxidising agentused in the impact initiated pyrotechnic composition. Perchlorates maybe used.

Typically, the impact initiated pyrotechnic composition and thesecondary pyrotechnic composition are blended together. The blend ratiomay be in the range 1.5:1 to 4:1 by weight of impact initiatedpyrotechnic composition to secondary pyrotechnic composition. Ingeneral, the impact initiated pyrotechnic composition and the secondarypyrotechnic composition are granular, and the grains are blendedtogether.

The impact initiated pyrotechnic composition may be disposed in front ofa resilient surface, the resilient surface being sufficiently resilientto resist the impact of the projectile to an extent which allowsinitiation of the impact initiated pyrotechnic composition to takeplace.

Without wishing to be bound by any particular theory, it is believedthat the resilience of the surface permits a compression of thepyrotechnic composition to occur upon impact which causes an increase intemperature which in turn causes the pyrotechnic composition to ignite.Depending on the impact initiating pyrotechnic composition and theenvisaged implication, it may not be necessary to utilise a resilientsurface in order to obtain impact initiation. The target may include ahousing, in which the resilient surface acts as a backing plate of thehousing, the backing plate having a wall upstanding therefrom forming anenclosure in which the impact initiating pyrotechnic composition isdisposed. Typically the backing plate and wall are formed from a metal,such as aluminium. The housing may further include a lid which isdisposed over the wall so that the housing fully encloses the impactinitiating pyrotechnic composition. The lid may be formed from sheetmaterial such as card or paper.

The compositions may be in granular form, in which instance a millingtechnique may be used to produce the granules. Alternatively, thecompositions may be produced using a slurry of the constituents which issubsequently dried.

The targets of the invention may be used as targets for firearms,air-operated arms such as air rifles and air pistols, or even inarchery. The targets may be intended for use as essentially a statictarget, in which instance the targets may consist essentially of thehousing described above. Alternatively, the targets may be a movingtarget such as a clay pigeon.

According to a second aspect of the invention there is provided a solidimpact initiated pyrotechnic composition including:

an oxidising agent;

optionally, a fuel or reducing agent;

a sensitiser in the form of a sulfur containing compound; and

optionally, a binder.

According to a third aspect of the invention there is provided the useof a solid impact initiated pyrotechnic composition of the second aspectof the invention as an impact initiated pyrotechnic.

According to a fourth aspect of the invention there is provided the useof a solid impact initiated pyrotechnic composition according to thesecond aspect of the invention in an impact initiated pyrotechnic targetfor signalling a strike by an impacting inert projectile.

Whilst the invention has been described above, it extends to anyinventive combination or sub-combination of the features set out aboveor in the following description or drawings or claims.

Embodiments of targets and compositions in accordance with the inventionwill now be described with reference to the accompany drawing whichshows

(a) an exploded view

(b) a perspective view

(c) a cross-sectional view of a target of the invention.

FIG. 1 depicts as housing of the invention, shown generally at 10, whichcomprises a casing 12, an explosive powder 14, and a lid 16. The casing12 comprises a circular backing plate 12 a and a peripheral circularwall 12 b upstanding therefrom. The casing 12 is formed from a suitablemetal, such as aluminium or steel. The casing 12 defines a cavity inwhich the explosive powder 14 resides. The lid 16 is formed from asuitable material, such as paper or card, and is positioned over theexplosive powder 14 by way of sealing against the upstanding wall 12 orby a friction fit with the upstanding wall 12.

In one example, the explosive powder contains an impact initiatedpyrotechnic composition which comprises 32% charcoal, 48% potassiumchlorate, 4% acaroid resin, and 16% thiourea with all percentages beingby weight. In a preferred embodiment, this composition acts as an“ignition composition”, and is used in conjunction with a secondary,“signal” composition which enhances the visual effect of a strike on thetarget by a projectile. The secondary “signal” composition may be asfollows:

Potassium perchlorate 66%, Aluminium Powder, 28%, and acaroid resin 6%,all percentages being by weight.

The two compositions are wet milled to achieve full incorporation andgranulated to form random cylindrical grains of varying lengths havingan average diameter of 1.7 mm. These dimensions and the integrity of thegrains are confirmed by separate screening, with over or under-sized orpoorly compacted grains being removed. The subsequent compaction withinthe housing further ensures that physical integrity is maintained. Atypical blend is 70% by weight of the ignition composition and 30% byweight of the signal composition.

When used in a target of the invention, the blended compositiondescribed above is capable of being impacted initiated by a projectileand provides a slow burning, bright but gentle white flame with a whitesmoke signature. The effect is not dissimilar to a theatrical stageeffect with sparks produced and incandescent debris projected up to 1 mof the firing point. Greater or lesser effects can be produced asdesired.

In representative examples, the target has a diameter range 40-90 mm anda depth in the range 10-15 mm, with the charge weight of the blendedcomposition being 8 g or less. However, it will be understood thattargets of the invention may be smaller or larger than these dimensions,and that different charges will be used in accordance with the precisenature of the composition and intended application.

The present invention also provides moving targets such as clay pigeontype targets. A clay pigeon target may incorporate one or more housingsfor the pyrotechnic composition which may be similar to the housing inFIG. 1 or at least share some similar constructional principles. Furtherdetails concerning the construction of these and other moving targetscan be found in WO02/35175, the entire contents of which are hereinincorporated by reference. Alternatively, it may be possible to produceclay pigeon targets which do not require the use of a housing to containthe pyrotechnic composition therein.

1. An impact initiated pyrotechnic target including an impact initiatedpyrotechnic composition which can be initiated by the impact of an inertprojectile, the pyrotechnic composition including: an oxidising agent;optionally, a fuel or reducing agent; a sensitiser in the form of asulfur containing compound; and optionally, a binder.
 2. An impactinitiated pyrotechnic target according to claim 1 in which thesensitiser is thiourea.
 3. An impact initiated pyrotechnic targetaccording to claim 1 in which the oxidising agent is a chlorate.
 4. Animpact initiated pyrotechnic target according to claim 3 in which theoxidising agent is potassium chlorate.
 5. An impact initiatedpyrotechnic target according to claim 1 in which the fuel or reducingagent is charcoal.
 6. An impact initiated pyrotechnic target accordingto claim 1 in which impact initiated pyrotechnic composition includes,by weight, 30-70% of the oxidising agent, 0-60% of the fuel or reducingagent, 8-40% of the sensitiser, and 0-15% of the binder.
 7. An impactinitiated pyrotechnic target according to claim 1 in which the binder isa resin.
 8. An impact initiated pyrotechnic target according to claim 1,further comprising a secondary pyrotechnic composition which isformulated to be initiated by the impact initiated pyrotechniccomposition to produce a desired signalling effect.
 9. An impactinitiated pyrotechnic target according to claim 8 in which the secondarypyrotechnic composition includes metal particles and an oxidising agent.10. An impact initiated pyrotechnic target according to claim 8 in whichthe secondary pyrotechnic composition is blended with the impactinitiated pyrotechnic composition.
 11. An impact initiated pyrotechnictarget according to claim 1 in which the impact initiated pyrotechniccomposition is disposed in front of a resilient surface, the resilientsurface being sufficiently resilient to resist the impact of theprojectile to an extent which allows initiation of the impact initiatedpyrotechnic composition to take place.
 12. An impact initiatedpyrotechnic target including: a housing, the housing comprising aresilient surface acting as a backing plate of the housing, wherein thebacking plate includes a wall upstanding therefrom forming an enclosure;and an impact initiated pyrotechnic composition disposed in theenclosure, the impact initiated pyrotechnic composition comprising: anoxidising agent optionally, a fuel or reducing agent; a sensitiser inthe form of a sulfur containing compound; and optionally, a binder. 13.An impact initiated pyrotechnic target according to claim 12 in whichthe housing further includes a lid which is disposed over the wall sothat the housing fully encloses the impact initiated pyrotechniccomposition.
 14. A solid impact initiated pyrotechnic compositionincluding: an oxidising agent; optionally, a fuel or reducing agent; asensitiser in the form of a sulfur containing compound; and optionally,a binder, wherein the solid impact initiated pyrotechnic compositionsignals a strike by an impacting projectile.
 15. (canceled) 16.(canceled)
 17. (canceled)
 18. An impact initiated pyrotechnic targetaccording to claim 14, wherein the impacting projectile is inert.
 19. Animpact initiated pyrotechnic target according to claim 8, in which theimpact initiated pyrotechnic composition is disposed in front of aresilient surface, the resilient surface being sufficiently resilient toresist the impact of the projectile to an extent which allows initiationof the impact initiated pyrotechnic composition to take place.
 20. Animpact initiated pyrotechnic target according to claim 8 in which thesensitiser is thiourea.
 21. An impact initiated pyrotechnic targetaccording to claim 8 in which the oxidising agent is a chlorate.
 22. Animpact initiated pyrotechnic target according to claim 8 in which thefuel or reducing agent is charcoal.
 23. An impact initiated pyrotechnictarget according to claim 1 in which the binder is an acaroid resin.